Sulfur trioxide (SO₃) is a colorless, corrosive liquid that is primarily used in the production of sulfuric acid, one of the most important industrial chemicals. It is formed by the oxidation of sulfur dioxide (SO₂) in the presence of oxygen. Due to its highly reactive nature, sulfur trioxide can react with water to produce sulfuric acid, releasing heat in the process. In the atmosphere, sulfur trioxide can contribute to the formation of acid rain when it reacts with moisture. This compound is also a significant pollutant, as it can lead to environmental issues such as respiratory problems in humans and damage to ecosystems. Proper handling and storage are essential to prevent accidents and exposure.